Aromatic polyamide pulp by means of continuous transferable polymerization-orientation method and a process for preparation thereof

ABSTRACT

A process for the preparation of aromatic polyamide pulp having both excellent physical properties and a high degree of polymerization by continuous polymerization and orientation by using of mixed solutions. The solutions are prepared by reacting diamine with aromatic diacid dichloride in an amide and/or urea-based polymerization solvent containing inorganic salts, or a mixture of inorganic salts and a Lewis acid compound. The process can be practiced by polymerization-orientation apparatus located on the continuous transferable polymerization-orientation means comprised of a belt and one or more stirring bars.

TECHNICAL FIELD

The present invention relates to a process for preparing aromaticpolyamide pulp. More particulary, the invention relates to a process forthe preparation of polyamide pulp having both excellent physicalproperties and a high degree of polymerization wherein an aromaticdiamine is reacted with aromatic diacid dichloride in an amide and/orurea-based polymerization solvent containing inorganic salts, or amixture of inorganic salts and a Lewis acid compound.

BACKGROUND ART

U.S. Pat. No. 4,511,623 discloses a process for preparing an aromaticpolyamide using solvent mixture of comprising inorganic salts wherein atertiary amine is added into the amide solvent system.

According to this method, polyamide fibers are prepared by addingtertiary amines prior to polymerization and applying a high mechnicalshear rate at the moment gelation is achieved, thus rapidly increasingthe rate of polymerization and producing a high degree of orientationand a high degree of polymerization.

But, because U.S. Pat. No. 4,511,623 adds the amide solvent and excesstertiary amines simultaneously, and adds the diacid dichloride all atonce, the viscosity of the reaction mixture suddenly increases whilepolymerization is occurring. Accordingly, polymerization is rapidlyterminated (within 10 seconds) and control of the process becomes verydifficult. In fact, it is impossible to continuously produce fibers,particularly fibers having a high degree of polymerization which cantake 5 hours.

In order to overcome the problems of the prior art the present inventorsdiscovered a process for producing pulp comprising extruding a liquidcrystalline pre-polymer (LCP) through an orientation unit, spraying, andcontact with a tertiary amine solvent system (e.g., Korean publishedpatent 90-4911). However, because gelation of polymer solution in thisprocess is initiated by the wall surface of the orientation unit theorientation unit becomes clogged, and control of the process becomesdifficult.

U.S. Pat. No. 5,106,560 discloses a process for the preparation of pulpby providing a polymerization solution of diacid dichloride, diamine andinorganic salts in an amide solvent system, followed by pouring thesolution on a inclined support to provide orientation by means ofgravity-induced shear forces. However, by using natural gravitymolecular orientation it is impossible to produce pulp having a highdegree of orientation.

U.S. Ser. No. 07/87,565 (filed Apr. 28, 1992 by the present inventors)discloses a method wherein an anisotropic polymerizing solution iscontinuously ejected into container, where it remains to mature.Unfortunately, this method has the same drawback as U.S. Pat. No.5,106,560 which provides orientation by means of gravity-induced shearforces in that a relatively low degree of orientation is achieved.

When an anisotropic polymerization solution having low inherentviscosity is ejected according to U.S. Ser. No. 07/87,565, theproperties of the final product are poor, and it takes approximately0.5˜5 hrs to increase the inherent viscosity and degree of orientationof the polymerizing solution. Similarly, the degree of molecularorientation obtained by means of gravity shear is lower than thatobtained by means of stirring, which results in decreased fibril growthin the final pulp and an increase in the time required for growth offibrils having acceptable specific surface areas due to the low degreeof orientation. Further, the properties of final product (e.g., asfriction materials or gaskets) which are made from such a final pulp arepoor.

Generally, in the case of friction materials containing fibers, thefriction effect applied to a matrix is increased with an increase in thespecific surface area of the fiber while the adhesion effect increasesas the length of pulp increases; these behaviors are considered to bemutually compromising factors, and lead to the use of powders which havehigh friction efficiencies due to a high surface area but provide lowmaterial reinforcement.

Therefore, when the degree of orientation of the molecular chain ishigh, the specific surface area can be increased by the formation offibrils, and the pulp has enough its length to reveal high adhesioneffect. But if the degree of orientation is low, the length of pulp isnot sufficient to increase the adhesion effect for final materials,while the specific surface area is increased due to the powder form.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide an aromaticpolyamide pulp wherein the aforesaid problems of prior art are avoided.

It is also an object of the present invention to provide aromaticpolyamide pulp by an easy, stable and cheap process without usingexpensive tertiary amines and which avoids process line solidificationproblems due to gelation.

Another object of the invention is to continuously provide a highmolecular weight aromatic polyamide pulp having excellent microfibrilgrowth and sufficient length to be utilized as reinforcement materials.

To achieve the aforesaid objects, the present invention provides aprocess for the preparation of aromatic polyamide pulps having repeatingunits represented by the following formula (A). ##STR1## wherein R₁, R₂are selected from the group consisting of the following aromatic groups,##STR2## X is H, Cl, Br, ##STR3## or alkyl or alkoxy group of from 1 to4 carbon atoms, Y is ##STR4##

Other and further objects, features and advantages of the invention willappear more fully in the following description.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates diagrammatically a preferred process in accordancewith the present invention.

FIG. 2(A) is a front view of FIG. 1

FIG. 2(B) is a plan view of the apparatus of FIG. 1

FIG. 3 is a front view of the belt part of FIG. 1

FIG. 4 and FIG. 5 represent depictions of ejector of raw material intomixer and a step of the first and second feeding.

(A) air layer (B) aromatic diamine solution

(C) The first aromatic diacid solution

(D) The first mixed solution

(E) The second aromatic diacid solution

BEST MODE FOR CARRYING OUT THE INVENTIONS

In the present invention, aromatic polyamide pulp is prepared by thefollowing process;

(a) providing a polymerization solvent by adding one or more inorganicsalts into amide-based or urea-based organic solvent system or into amixture of amide-based and urea-based organic solvent system;

(b) preparing a first solution by dissolving one or more aromaticdiamines in said polymerization solvent, and then adding 20˜50 wt % of atotal 100 wt % amount of one or more aromatic diacid dichlorides whichwill react with the one or more aromatic diamines in equivalent moles;

(c) adding said first solution and the remainder 50˜80 wt % of the oneor more aromatic diacid dichloride to a continuous mixer simultaneouslywith mixing, and then ejecting said mixed solution onto a means forcontinuous transferable polymerization-orientation;

(d) polymerizing and orienting said mixed solution obtained in step (c)by polymerization orientation means located on the continuoustransferable polymerization-orientation means;

(e) maintaining and maturing the polymerized and oriented mixed solutionobtained in (d) at a predetermined temperature for a predetermined timein the continuous transferable polymerization-orientation system;

(f) precipitating the material obtained in (e) above into aprecipitating solution, and then pulverizing and drying the precipitatedmaterial in a pulping means.

The present invention is explained in more detail as follows:

1) Preparation of the Polymerization Solvent

In the present invention, amide-based or an urea-based organic solventsystem, or mixture thereof, are used as the polymerization solvent. Anywt % mixture may be used.

Preferred amide-based or urea-based organic solvents used in theinvention include, for example, N-methyl-2-pyrrolidinone (NMP),N,N-dimethyl acetamide (DMAc), hexamethylphosphoamide (HMPA),N,N-dimethylformamide (DMF), N,N,N',N'-tetramethylurea (TMU) orcombinations thereof.

One or more inorganic salts may be added to the above organic solventsystem in order to increase the solubility of the eventual polymer.Preferred inorganic salts include metal halides or alkali earth metalhalide salts such as CaCl₂, LiCl, NaCl, KCl, LiBr, KBr. A single salt ora mixture of inorganic salts may be added.

The amount of inorganic salts added to the solvent is preferably lessthan 12 wt % based on the total weight of polymerization solvent.

When the amount of inorganic salts is more than 12 wt %, it is noteconomical becuase further desired effects are not achieved.

A small amount of one or more Lewis acids may be added to thepolymerization solvents in addition to the inorganic salt(s) in order tofurther increase the solubility of the polymer. Preferred Lewis acidcompounds are selected from the group consisting of compounds of halogenatoms and transition metals, and compounds of halogen atoms and GroupIIIA, IVA, VA, and VIA atoms of the periodic table, including BF₃, BCl₃,AlCl₂, MgCl₃, FeCl₂, FeCl₃, ZnCl₂, SbCl₂ and HgCl₂. The amount of Lewisacid added is preferably from 0.1 to 5 wt % on the basis of the totalweight of polymerization solvent.

When the amount of Lewis acid is less than 0.1 wt %, the increase in thesolubility of the final polymer and its molecular weight is no more thanthat obtained with the simple addition of inorganic salts.

When the amount of Lewis acid is more than 5%, while the solubility andmolecular weight is increased, it is not economical.

According to the present invention, when mixtures of inorganic salts areused with Lewis acids, the inherent viscosity of the solution isincreased due to an increase in solubility as compared with the case ofusing only inorganic salt(s).

2) Preparation of the First Solution

After an aromatic diamine solution is prepared by dissolving one or morearomatic diamines in the above-described polymerization solvent, thearomatic diamine solution is transferred to a mixer set at apredetermined temperature using a quantitative pump and temperaturecontroller, and simultaneously 20 to 50 wt % of a total 100 wt % of oneor more aromatic diamine in equivalent moles, is added thereto mixed,and reacted. The process of adding the aromatic diacid dichloride(s) ispreferably carried out at a temperature of from 0 to 30° C.

The above first mixed solution (solvent, polyamide and some diaciddichloride) and remainder 50 to 80 wt % of aromatic diacid dichloride(s)are then simultaneously added to a continuous mixer using a pump and atemperature controller and mixed to provide a second mixed solution, andthen the mixture is ejected onto means for continuous transferablepolymerization-orientation, where it is stirrred and polymerized.

In the above process, it is possible to add all the aromatic diaciddichloride at once, but because mixing is not achieved uniformly due toan abrupt reaction and because side reactions have an effect on theproperties of the final product, it is preferable to add it in twostages as above in order to obtain a uniform mixture.

In order to obtain a uniform mixture in a short time, it is preferableto add the reactants together in same direction (parallel direction) byusing an ejector like that represented in FIG. 4 and FIG. 5 when thefirst mixed solution and the remainder of aromatic diacid dichloride areadded together and/or to the continuous mixer.

Generally it takes approximately 1˜30 sec to mix the above reactants ina continuous mixer. Therefore, the present invention does not require aspecial polymerization reactor as prior art methods do to make possiblethe production of large quantities.

3) Polymerization, Orientation and Maturing of the Mixed Solution

The second mixed solution is ejected onto means for continuoustransferable polymerization-orientation at a predetermined temperature,and the solution is stirred, optionally continuously, usingpolymerization-orientation means to increase the degree ofpolymerization and provide orientation (in the rotating direction). Theaverage shear rate of the polymerization-orientation means is preferablymore than 10/sec.

Referring now to the drawings, a continuous transferablepolymerization-orientation system in accordance with the presentinvention is illustrated in FIG. 1 to FIG. 3.

The polymerization-orientation apparatus (circled) of the continuoustransferable polymerization-orientation system of FIG. 1 can be movedfrom front to rear, and the rpm of all driving motors (1) can becontrolled variably. The polymerization-orientation apparatus is fixedat a predetermined place on the system while belt (4) is moving at lowspeed to polymerize and provide orientation.

A guide (8) may be attached to both edges (6) of the belt to prevent thepolymer solution from flowing to the side (5) of the belt and guide (7)may be located on the back edge of the belt to prevent the ejectedpolymer solution from flowing in the opposite direction of the beltprogress direction.

Polymerization and orientation by stirring in the continuoustransferable polymerization-orientation system is achieved within theturning radius of the rotating plate (2) of polymerization orientationapparatus. More than one polymerization-orientation stirring bar (3) canbe used, and is assembled so that attachment and detachment is easy.Further, it is possible to use two or more polymerization-orientationapparatuses to polymerize and orient.

The obtained polymer, which is polymerized and oriented by stirring, ismaintained on the continuous transferable polymerization-orientationsystem (e.g., on the belt) and matured at a temperature of from 25° to100° C., for preferably 10 to 60 mins to increase the inherent viscosityand the degree of orientation of the polymer. When the maturingtemperature is less than 25° C., the time required for maturing isextended and when it is more than 100° C., the inherent viscosity of thefinal pulp is decreased.

The concentration of polymer is preferably about 3 to 15% by weight ofthe polymerizing solvent. When the concentration of polymer is less than3% by weight, it is not economical due to the low concentration althoughit is possible to produce a pulp having high inherent viscosity, andwhen the concentration of polymer exceeds 15% by weight, solubility isdecreased and it is difficult to prepare a pulp having a high inherentviscosity.

4) Preparation of the Pulp

Matured polymer is precipitated into a precipitating solution and thenadded to pulping means (10), pulverized and dried to prepare polyamidepulp.

The precipitating solution of the present invention is preferably wateror a basic aqueous solution, or a mixture of one of the aboveprecipitating solutions and the polymerization solvent. A basic aqueoussolution is used in order to remove the HCl gas generated in thepolymerization reaction and to neutralize the system to prevent theinherent viscosity of polymer from decreasing due to the presence ofacid and to prevent the apparatus from corroding. The object of usingthe mixture of precipitating solution and polymerization solvent is tocontrol the extraction rate of polymerization solvent to reduce the timerequired for pulping and to promote microfibril growth. Preferred basicaqueous solutions are aqueous solutions selected from the groupconsisting of NaOH, KOH, Na₂ CO₃, K₂ CO₃, NaHCO₃, Ca(OH)₂, and CaO. Theconcentration of these aqueous solutions is preferred to be from 0.1 to20% by weight in order to obtain neutralization and increased viscosity.

When using a mixed precipitating solution, the amount of thepolymerization solvent is preferably less than 50% by weight of thetotal precipitating solvent. When the amount of the polymerizationsolvent is more than 50% by weight, the extraction rate of the solventis decreased and provides a bad pulp shape.

Any conventional pulping machine can be used as the pulping means of thepresent invention.

According to the above method, an aromatic polyamide pulp havingrepeating units represented by formula (A) can be prepared: ##STR5##wherein R₁, and R₂ are selected from the group consisting of thefollowing aromatic groups, ##STR6## X is H, Cl, Br, ##STR7## I or alkylor alkoxy group of from 1 to 4 carbon atoms, Y is ##STR8## and where R₁is the aromatic group of the aromatic diamine, and R₂ is the aromaticgroup of the aromatic diacid dichloride.

The inherent viscosity (I.V.) of the pulp prepared by the presnetinvention is preferably more than 3.0 g/dl and the Canadian StandardFreeness is preferably within the range of 650 to 400 ml, and the lengthdistribution as measured by BAUER-McNETT classifier is preferably

14 mesh or more is less than 30%,

28 mesh or more is more than 30%,

48 mesh or more is more than 60%,

100 mesh or more is more than 70%,

150 mesh or less is less than 25%,

where the screen mesh sizes are of the Tyler series and where theCanadian Standard Freeness and length distribution were measured byTAPPI T227 om-85 and TAPPI 233 om-82, respectively.

One of the main effects of the present invention is to increase thedegree of polymerization and orientation in a short amount of time byutilization of a polymerization-orientation apparatus in a continuoustransferable polymerization-orientation system without using expensiveand harmful tertiary amines.

In conventional methods, it is impossible to orient continuoulsy a highviscosity polymer solution because gelation occurs due to abruptreaction in the reactor, and the orientation apparatus is clogged bygelation.

The present invention solves the problem of gelation on a process linebecause polymerization and orientation is carried out in open means suchas on a belt without using a closed system such as a polymerization tankor a polymerization reactor like conventional polymerization andorientation apparatuses.

Further, the present invention can control the polymerizationtemperature while reducing the energy consumption which is essential inthe prior art to cool the polymerization reactor to low temperature dueto the exothermic reaction in conventional methods, and can orient highviscosity solutions easily and continuously. One reason the presentprocess is able to orient high viscosity solutions is that it ispossible to maintain the effect of molecular orientation by stirring ifthe stirring is continued until the polymer is gelled. If molecularorientation is achieved by shear force, and then the shear force isremoved before gelling, molecular orientation is lost and extremely lowviscosity is obtained. Because in the present invention, orientation iscontinued until the polymer is gelled, the polymer does not return tothe inordered state and obtains maximum orientation.

With the present invention, it is possible to reduce the time requiredfor pulping due to the maximum orientation obtained and produce highmicro-fibrillated aromatic polyamide pulp cheaply and continuously.

This invention is illustrated by the following Examples, but should notconstrued to be limited thereto.

The inherent viscosity (I.V.) of the pulp prepared invention iscalculated by following equation.

    I.V.(g/dl)=1n(η.sub.rel)/C

Wherein C is the concentration of polymer solution (5.0 g of polymer isdissolved in 100 ml of 95˜98% conc. sulfuric acid), and relativeviscosity η_(rel) is the ratio of flowing time measured by capillaryviscometer using 95˜98% conc. sulfuric acid as solvent.

EXAMPLE 1

After the temperature of a reactor in which 700 kgN-methyl-2-pyrrolidinone was added was controlled to 70°, 56 kg of CaCl₂was added thereto, stirred and completely dissolved.

To the above polymerization solvent was added 29.97 kg of p-phenylenediamine, stirred and dissolved to prepare the solution of aromaticdiamine.

The above amine solution was added at the rate of 785.97 g/min using aquantitative pump to a mixer controlled at a temperature of 10° C. usinga temperature controller, and, simultaneously, melted terephthaloylchloride was added thereto at the rate of 19.69 g/min and mixed andreacted to prepare a first mixed solution.

To a continuous mixer, the first mixed solution and more meltedterephthaloyl chloride was added at rates of 805.66 g/min and 36.57g/min, respectively.

After the resulting solution was stirred in the continuous mixer for 10sec, the mixed solution was fed into a continuous transferablepolymerization-orientation system through an opening at a temperature of50° C., and stirred and mixed at the shear rate of 20/sec to polymerizeand orient until gelation was completed, and then maintained there for30 mins and matured.

After the above solidified polymer was isolated from the continuoustransferable polymerization-orientation system, it was precipitated intowater and fed to a pulping machine, pulverized and dried to prepare apulp.

The inherent viscosity of the pulp was 4.5, and Canadian StandardFreeness was 641 ml and the length distribution was, 14 mesh 29%, 28mesh 22%, 48 mesh 36%, 100 mesh 5% and 150 mesh less than 8%.

EXAMPLE 2˜9

The same procedure was carried out as described in Example 1 with theamount of components, conditions and properties provided in Table 1.

                  TABLE 1                                                         ______________________________________                                               Polymerization solvent                                                                   Amount                                                             Liquid     of        Lewis Acid                                                          Amount  CaCl.sub.2    Amount                                Example  Type     (kg)    (kg)    Type  (kg)                                  ______________________________________                                        1        NMP      700     56      --    --                                    2        NMP      700     56      --    --                                    3        NMP      800     60      --    --                                    4        NMP      800     50      AlCl.sub.3                                                                          10                                    5        NMP      600     50      --    --                                    6        NMP      700     56      --    --                                    7        NMP      800     60      --    --                                    8        NMP      800     60      --    --                                    9        NMP      800     30      MgCl.sub.2                                                                          10                                    ______________________________________                                        Mixing                                                                        1st solution        Final Solution                                            amine solution  Amount  1st solution Amount                                          Temp.    Amount  (g/   Temp.  Amount                                                                              (g/                                Example                                                                              (°C.)                                                                           (g/min) min)  (°C.)                                                                         (g/min)                                                                             min)                               ______________________________________                                        1      10       785.    16.69 5      805.  36.57                                              97                   66                                       2      10       785.    16.88 5      802.  39.38                                              97                   85                                       3      10       889.    22.50 5      912.  33.76                                              97                   47                                       4      5        889.    19.69 5      909.  36.57                                              97                   66                                       5      10       679.    11.25 5      691.  45.01                                              97                   22                                       6      10       785.    11.25 5      787.  45.01                                              97                   22                                       7      10       889.    19.69 5      909.  36.57                                              97                   66                                       8      10       889.    16.88 5      906.  39.38                                              97                   85                                       9      5        869.    16.88 5      886.  39.38                                              97                   85                                       ______________________________________                                               P/O system                                                                    shear                                                                         rate    gelation                                                                (1/       Temp   Time     Pulverizing                                Example  sec)      (°C.)                                                                         (min     solvent                                    ______________________________________                                        1        20        50     30       water                                      2        40        60     30       aq. NaHCO.sub.2                            3        60        60     60       30% polyn. sol.                                                               70% water                                  4        140       60     60       20% polyn. sol.                                                               80% water                                  5        120       60     60       30% polyn. sol.                                                               70% water                                  6        180       50     50       90% polyn. sol.                                                               10% water                                  7        100       60     60       20% polyn. sol.                                                               80% water                                  8        60        60     60       aq. Ca(OH).sub.2                           9        100       30     30       water                                      ______________________________________                                        Properties                                                                                  Length Distribution                                                                     more  more more more  less                                           Canadian than  than than than  than                                           Standard 14    28   48   100   150                                            Freeness mesh  mesh mesh mesh  mesh                            Example I.V.   (ml)     (ml)  (%)  (%)  (%)   (%)                             ______________________________________                                        1       4.5    641      29    22   36    5    8                               2       4.7    628      29    20   36    5    10                              3       5.8    602      23    21   36   11    9                               4       6.4    547      28    20   21   12    14                              5       4.1    497      26    17   28   14    15                              6       5.2    468      25    24   24   15    12                              7       5.9    582      22    17   38   10    13                              8       5.3    613      --    --   --   --    --                              9       4.0    647      --    --   --   --    --                              ______________________________________                                         NMP: Nmethyl-2-pyrollidone,                                                   TPC: Terephthaloyl chloride,                                                  P/O system: polymerizationorientation system                                  polyn. sol.: polymerization solvent                                      

<<COMPARATIVE EXAMPLE 1>>

After the temperature of a reactor in which 700 kgN-methyl-2-pyrrolidinone (NMP) was added was controlled to 70° C., 56 kgof CaCl₂ was added, stirred and completely dissolved.

To the above polymerization solvent was added 29.97 kg of p-phenylenediamine, stirred and dissolved to prepare the solution of aromaticdiamine.

The above amine solution was added at the rate of 785.97 g/min usingquantitative pump to the mixer and controlled at the temperature of 10°C. using temperature controller, and simultaneously melted terephthaloylchloride was added thereto at the rate of 19.69 g/min and mixed andreacted to prepare the first mixed solution.

To a continuous mixer, the first mixed solution and more meltedterephthaloyl chloride was added at the rates of 805.66 g/min and 36.57g/min, respectively and mixed for 10 sec.

The temperature of the polymer inside the continuous mixer wascontrolled not to exceed 60° C.

The above mixed solution was continuously ejected onto a moving beltprovided at the bottom of opening, and maintained thereon for 50 minsand matured.

The above solidified polymer was precipitated into 30% (NMP) solution ofpolymerization solvent and fed to the same pulping machine used inExamples 1˜9, pulverized and dried to prepare a pulp as powder form.

The inherent viscosity of the pulp was 1.8.

<<COMPARATIVE EXAMPLE 2>>

After the temperature of reactor in which 700 kgN-methyl-2-pyrrolidinone was added was controlled at 70° C., 56 kg ofCaCl₂ was added, stirred and completely dissolved.

To the above polymerization solvent was added 29.97 kg of p-phenylenediamine, stirred and dissolved to prepare the solution of aromaticdiamine.

The above amine solution was added at a rate of 785.97 g/min using aquantitative pump to a mixer and controlled at the temperature of 10° C.using temperature control, and simultaneously melted terephthaloylchloride was added thereto at a rate of 19.69 g/min and reacted toprepare a first mixed solution.

The first mixed solution and more melted terephthaloyl chloride wereadded at the rates of 805.66 g/min and 36.57 g/min, respectively on amoving belt, at a temperature of 60° C., and maintained there for 50mins and matured.

The above mixed solution on the belt was not solidified and wasprecipitated into 30% NMP solution of polymerization solvent and fed tothe pulping machine of Example 1, pulverized and dried.

The inherent viscosity of the pulp as powder form was 0.3.

<<COMPARATIVE EXAMPLE 3>>

After the temperature of reactor in which 600 kgN-methyl-2-pyrrolidinone was added was controlled at 70° C., 50 kg ofCaCl₂ was added, stirred and completely dissolved.

To the above polymerization solvent was added 29.97 kg of p-phenylenediamine, stirred and dissolved to prepare the solution of aromaticdiamine.

The above solution was added at a rate of 679.97 g/min using aquantitative pump to a mixer and controlled at a temperature of 10° C.using temperature control, and simultaneously melted terephthaloylchloride was added thereto at the rate of 14.07 g/min and mixed andreacted to prepare the first mixed solution.

To the continuous mixer, the first mixed solution and meltedterephthaloyl chloride was added at rates of 694.04 g/min and 42.19g/min, respectively and mixed for 10 sec. The temperature of the polymerinside the continuous mixer was controlled not to exceed 60° C.

The above mixed solution was continuously ejected on a moving beltprovided at the bottom of opening, and then maintained there for 50 minsand matured.

The above solidified polymer was precipitated into 30% NMP solution ofpolymerization solvent and fed to the pulping apparatus of Example 1,pulverized and dried to prepare a pulp as powder form.

The inherent viscosity of the pulp was 1.6.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A process for the preparation of aromaticpolyamide pulp, which process comprises the steps of: urea-containingsolvent, or a mixture thereof, and mixing therewith 20 to 50 wt % of oneor more aromatic diacid dichlorides;(c) adding said first mixture andthe remainder 50 to 80 wt % of aromatic diacid dichloride to acontinuous mixer simultaneously with mixing, and then ejecting saidmixed solution onto a continuous transferable polymerization-orientationmeans; (d) polymerizing and orienting said mixed solution obtained in(c) by polymerization orientation means located on the continuoustransferable polymerization-orientation means; (e) maintaining andmaturing said polymerized and oriented mixed solution obtained in (d) inthe continuous transferable polymerization-orientation means; (f)precipitating the material obtained in (e) into a precipitatingsolution, and then pulverizing and drying the precipitate in pulpingmeans; (g) obtaining an aromatic polyamide pulp having repeating unitsrepresented by the following formula (A): ##STR9## wherein R₁, R₂ areselected from the group consisting of the following aromatic groups,##STR10## X is H, Cl, Br, ##STR11## or alkyl or alkoxy group of from 1to 4 carbon atoms, Y is ##STR12##
 2. An aromatic polyamide pulp havingan inherent viscosity of more than 4.7 g/dl and a Canadian StandardFreeness of less than 650 ml.
 3. The aromatic polyamide pulp accordingto claim 2, wherein said aromatic polyamide ispoly(p-phenyleneterephthalamide).
 4. An aromatic polyamide pulp havingan inherent viscosity of more than 3.0 g/dl, a Canadian StandardFreeness of less than 650 ml and a pulp length distribution at 14 meshor more or less than 30%, at 28 mesh or more of more than 30%, at 48mesh or more of more than 60%, at 100 mesh or more of more than 70%, andat 150 mesh or less of less than 25%.
 5. The aromatic polyamide pulpaccording to claim 4, wherein said aromatic polyamide ispoly(p-phenyleneterephthalamide).
 6. The process of claim 1, whereinsaid polymerization solvent further comprises one or more inorganicsalts.
 7. The process according to claim 1, wherein said organicsolvents are selected from the group consisting ofN-methyl-2-pyrrolidinone, N,N-dimethylacetamide, hexamethylphosphoamide,N,N-dimethylformamide, N,N,N',N'-tetramethylurea, and mixtures thereof.8. The process according to claim 6, wherein said inorganic salts areselected from the group consisting of CaCl₂, LiCl, NaCl, KCl, LiBr, KBr,and mixtures thereof.
 9. The process according to claim 8, wherein theamount of said inorganic salts is 0.1 to 12% by weight of saidpolymerization solvent.
 10. The process according to claim 1, where oneor more Lewis acid compounds is added to said polymerization solvent.11. The process according to claim 10, wherein said one or more Lewisacid compounds is selected from the group consisting of BF₂, BCl₃,AlCl₃, MgCl₂, FeCl₂, FeCl₃, ZnCl₂, SbCl₂, HgCl₂, and mixture thereof.12. The process according to claim 10, wherein the amount of said one ormore Lewis acid compounds is 0.5 to 5% by weight of said polymerizationsolvent.
 13. The process according to claim 1, wherein said aromaticdiamine/polymerization solvent solution and said 20˜50 wt % of saidaromatic diacid dichloride in step (b), and said first mixture and saidremainder aromatic diacid dichloride of step (c) are mixed in paralleldirection.
 14. The process according to claim 13, wherein said mixing isaccomplished with the ejector.
 15. The process according to claim 1,wherein said continuous transferable polymerization-orientation meanscomprises a belt and one or more stirring bars.
 16. The processaccording to claim 15, wherein said one or more stirring bars rotatearound an axis perpendicular to an upper surface of the belt.
 17. Theprocess according to claim 15, comprising plural stirring bars.
 18. Theprocess according to claim 15, wherein a guide is provided to preventsaid solution ejected from flowing in a direction opposite to theprogress of the belt.
 19. The process according to claim 15, whereinguides are provided at both edges of said belt to prevent said solutionfrom flowing to the side of said belt.
 20. The process according toclaim 15, wherein said one or more stirring bars are provided at anupper part of said belt.
 21. The process according to claim 1, whereinin step (c) said solution is ejected on the continuous transferablepolymerization-orientation means by free fall.
 22. The process accordingto claim 1, wherein the concentration of said polymer is 3 to 15% byweight of said total polymerization solution.
 23. The process accordingto claim 1, wherein polymerization and orientation is carried out untilthe polymer is gelled.
 24. The process according to claim 1, wherein instep (e) polymer solution is matured by maintaining said solution at atemperature of 25° to 100° C., for 10 to 60 mins.
 25. The processaccording to claim 1, wherein said precipitating solution is selectedfrom the group consisting of water, basic aqueous solution, and mixturesof one water or a basic aqueous solution with said polymerizationsolvent.
 26. The process according to claim 25, wherein said basicaqueous solution is selected from the group consisting of aqueoussolutions of NaOH, KOH, Na₂ CO₃, K₂ CO₃, NaHCO₂, Ca(OH)₂ and CaO. 27.The process according to claim 26, wherein the concentration of saidbasic aqueous solution is 0.1 to 20 wt %.
 28. The process according toclaim 25, wherein the amount of polymerization solvent in said mixedprecipitation solution is less than 50% by weight of said totalprecipitating solution.
 29. The process according to claim 1, whereinsaid aromatic polyamide is poly(p-phenylene terephthalamide).